Update the window labels if they change in overview mode.

ash/wm/overview/window_selector_item.h

Index: ash/wm/overview/window_selector_item.h
diff --git a/ash/wm/overview/window_selector_item.h b/ash/wm/overview/window_selector_item.h
index ac57266c12266fba0482d92dc692c8e82dbdb17a..9f1e021991472d05d7de8dd9284ec35090dc5e32 100644
--- a/ash/wm/overview/window_selector_item.h
+++ b/ash/wm/overview/window_selector_item.h
@@ -7,6 +7,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "ui/aura/window_observer.h"
 #include "ui/gfx/rect.h"
 #include "ui/views/controls/button/button.h"
 
@@ -24,7 +25,8 @@ class TransparentActivateWindowButton;
 // This class represents an item in overview mode. An item can have one or more
 // windows, of which only one can be activated by keyboard (i.e. alt+tab) but
 // any can be selected with a pointer (touch or mouse).
-class WindowSelectorItem : public views::ButtonListener {
+class WindowSelectorItem : public views::ButtonListener,
+                           public aura::WindowObserver {
  public:
   WindowSelectorItem();
   virtual ~WindowSelectorItem();
@@ -83,6 +85,10 @@ class WindowSelectorItem : public views::ButtonListener {
   virtual void ButtonPressed(views::Button* sender,
                              const ui::Event& event) OVERRIDE;
 
+  // aura::WindowObserver:
+  virtual void OnWindowTitleChanged(aura::Window* window,
+                                    const base::string16& title) OVERRIDE;
+
  protected:
   // Sets the bounds of this selector's items to |target_bounds| in
   // |root_window|. If |animate| the windows are animated from their current